1. Field of the Invention
The present invention relates, for example, to an optical disk device used for recording a signal in an optical disk or for reproducing a signal of an optical disk, a control method of an optical system, a medium, and an information aggregate.
2. Description of the Related Art
The configuration and action of a conventional optical disk device will be described on the basis of FIG. 1(A) to FIG. 1(C) and FIGS. 2, 7. FIG. 1(A), FIG. 1(B), and FIG. 1(C) are a cross-sectional configuration figure of a conventional optical head, a typical figure of optical detecting means 9, and a partial enlarged view showing grooves and pits formed on an optical disk signal surface and the position of an optical spot, respectively. Herein, the position of a pit 14c in FIG. 1(C) is on the inner peripheral side of an optical disk 8 from the positions of pits 14a, 14b. 
In FIG. 1(A), light 2 emitted from a radiating light source 1 such as a semiconductor laser penetrates a beam splitter 3, and is converted into parallel light 5 by a collimate lens 4. This light 5 is reflected on a reflecting mirror 6 and is condensed on a signal surface 8S formed on the rear surface of an optical disk 8 by an objective lens 7. In the objective lens 7, the focusing and tracking, and the tilt in the radial direction are controlled by an actuator. The light reflected on the signal surface 8S is condensed by the objective lens 7 and reflected on the reflecting mirror 6, and passing through the collimate lens 4, it is reflected on the beam splitter 3, and becomes light 10 to be condensed on optical detecting means 9.
The optical detecting means 9 is divided by a dividing line 9L corresponding to the rotational direction (direction Y at right angles to the paper surface of FIG. 1(A)) of the optical disk 8, and as shown in FIG. 1(B), this dividing line 9L approximately equally divides an optical spot 10S on the optical detecting means into two, and each difference signal 10S is detected by a subtracter 10, and a summation signal 11S is detected by an adder 11.
As shown in FIG. 1(C), on the signal surface 8S of the optical disk, uneven groves 13G and inter-groove spaces 13L, pit lines 14a and pit lines 14b with a fixed length are formed in cycles at a pitch p in the radial direction 12 of the optical disk 8. On the groove 13G and inter-groove space 13L, signal marks 15 having a reflection factor different from that out of the own area are formed, and the difference of those reflection factors is read as a reproduction signal by an optical spot 16 scanning along the groove and inter-groove space. The positions of the pit lines 14a, 14b are in synchronization with each other in the adjacent tracks, and they are also in cycles at a pitch q in the rotational direction of the optical disk. Furthermore, the center of the pit line 14a deviates from the center of the groove 13G by s along the radial direction, and the pit line 14b deviates by s in the opposite direction thereof. Accordingly, when the optical spot 16 that has been tracking-position-controlled on the groove 13G and the inter-groove space 13L scans on the pit lines 14a, 14b, each goes on a position deviating from the center of the pit by s.
On the other hand, on the inner peripheral side of the optical disk, pit lines 14c are formed in cycles at a pitch Pxe2x80x2 in the radial direction 12. It is possible that the positions of the pit lines 14c are not in synchronization with each other in the adjacent ones, and it is also possible that there is no periodicity in the rotational direction of the optical disk and the length is random. Naturally, when the tracking-position-controlled optical spot 16 scans on the pit line 14c, it goes on the center position of the pit.
FIG. 2 shows a signal waveform of a summation signal 11S at the time when the optical spot 16 scans near the pit lines 14a and 14b. Herein, in FIG. 2, the time-axis is shown in the horizontal axis, and it expresses the fact that the signal waveform of the pit line 14b is detected after the signal waveform of the pit line 14a has been detected. When the optical spot 16 is positioned at places 101a, 101b just beside the pits (refer to FIG. 1(c)), the scattering effect by the pit is large and the detected light quantity is lowered, but when it is positioned at places 102a, 102b just beside the inter-pit spaces (spaces between a pit and a next pit) (refer to FIG. 1(C)), the detected light quantity is restored. Accordingly, by scanning beside the pit line 14a, the reproduction signal vibrates between an envelope 17a (corresponding to the reproduction signal at the position 101a) and an envelope 18a (corresponding to the reproduction signal at the position 102a) (letting the output differences from a level 19 of a detected light quantity of zero to the respective envelopes be A1, A2). Similarly, by the scanning of the optical spot 16 beside the pit line 14b, the reproduction signal also vibrates between an envelope 17b (corresponding to the reproduction signal at the position 101b) and an envelope 18b (corresponding to the reproduction signal at the position 102b) (letting the output differences from a level 19 of a detected light quantity of zero to the respective envelopes be B1, B2).
FIG. 7 shows a flow of the control signal process in the movable tilting means of a conventional optical disk device. In FIG. 7, a summation signal 11S created in the adder 11 is a signal at the time when the optical spot 16 scans near the pit lines 14a and 14b, and it shows a signal waveform shown in FIG. 2. These signals whose detecting times are different are introduced into an arithmetic circuit 20, and the delaying process is applied, and a signal B defined by the relation of B=(A2xe2x88x92A1)xe2x88x92(B2xe2x88x92B1) is created, and a signal 23 in which the high frequencies are cut by a low-pass filter 22 is made.
On the other hand, a signal A of the difference created in the subtracter 10 is a signal at the time when the optical spot 16 scans on the groove 13G or the inter-groove space 13L. A difference signal 24 of this signal A and the signal 23 is introduced into a driving circuit 25, and a tracking drive signal 26 is created. By this drive signal 26, the objective lens 7 is moved in the radial direction of the optical disk 8, and according to the control formula B=0, the tracking center control of the optical spot 16 is performed.
Furthermore, under the condition where this tracking control is applied, the signal A becomes a signal 28 in which the high frequencies are cut by a low-pass filter 27 and is introduced into a driving circuit 29, and a lens tilt drive signal 30 is created. By this drive signal 30, the objective lens 7 is tilted in the radial direction of the optical disk 8 (state of the objective lens 7xe2x80x2 in FIG. 1(A)), and according to the control formula A=0, the lens tilt control is performed.
By such a control, it has been intended to reduce the off-track quantity of the optical spot 16 and to cancel the aberration (especially, third order coma aberration) of the optical spot 16 created by the tilt of the optical disk 8 (state of the optical disk 8xe2x80x2 in FIG. 1(A)).
However, actually, there has been such a problem that the off-track quantity cannot be made zero by a conventional method like this, and that the third order coma aberration also cannot be cancelled. Furthermore, it has been impossible to well understand the reason.
When the off-track quantity deviates from zero, there is such a problem that the optical spot 16 eliminates part of the adjacent signal mark 15 at the time of recording and that the cross-talk increases at the time of reproduction to degrade the jitter or the like. Furthermore, when the third order coma aberration cannot be cancelled, there are problems such as the power shortage at the time of recording or the degradation of the jitter at the time of reproduction.
Considering such problems, it is an object of the present invention to provide, for example, an optical disk device in which the off-track or the third order coma aberration created by the relative tilt of the disk can be suppressed to an extremely small degree, a control method of an optical system, a program recording medium, and an information aggregate.
One aspect of the present invention is an optical disk device comprising:
optical condensing means for condensing radiated light from a light source on an optical disk;
optical detecting means for detecting reflected light from said optical disk; and
control means for performing tracking control and/or tilt control of said optical condensing means by utilizing output from said optical detecting means, wherein said control means uses an off-track quantity and/or a tilt quantity of said optical condensing means, when said control is performed.
Another aspect of the present invention is an optical disk device comprising:
a radiating light source for performing radiation of a radiated light;
an objective lens for condensing said radiated light on a signal surface of an optical disk as an optical spot, and for condensing returning light from said optical disk;
movable tilting means for controlling movement of said objective lens in the radial direction of said optical disk, and tilt in said radial direction of said objective lens; and
optical detecting means for detecting a light quantity of said returning light, wherein
a signal A and a signal B that are detected when said optical spot scans near cyclic grooves or cyclic pits formed on a signal surface of said optical disk are compensated by using quantities
xcex2xc2x7LT and xcex3xc2x7LT proportional to a tilt quantity LT of said objective lens to be a compensated signal (A-xcex2xc2x7LT) and a compensated signal (B-xcex3xc2x7LT), and letting said compensated signal (A-xcex2xc2x7LT) be a tilt control signal for controlling tilt of said objective lens, and letting said compensated signal (B-xcex3xc2x7LT) be a tracking control signal for controlling an alignment to said cyclic grooves or said cyclic inter-groove spaces of said optical spot, said movable tilting means controls said movement of said objective lens and said tilt of said objective lens so that said tilt control signal and said tracking control signal may substantially be zero.
Still another aspect of the present invention is the optical disk device, further comprising optical distributing means for distributing said radiated light and said returning light, wherein said returning light is bent in a direction different from that on the approach route side of said radiated light by said optical distributing means and condensed on said optical detecting means.
Yet another aspect of the present invention is the optical disk device, wherein
said cyclic grooves and said cyclic pits are formed along the radial direction of said optical disk by a pitch P, and
in said cyclic pits, there are cyclic pits a arranged such that the positions thereof are shifted to the inner peripheral side along the radial direction from the positions of cyclic grooves by s in cycles in the rotational direction of the optical disk, and cyclic pits b arranged to be inversely shifted to the outer peripheral side by s in cycles in the rotational direction of said optical disk, and
said optical spot scans on said cyclic grooves or on said cyclic inter-groove spaces.
Still yet another aspect of the present invention is the optical disk device, wherein a positional shift s of said cyclic pits is equal to P/4 or P/2.
A further aspect of the present invention is the optical disk device, wherein a tilt quantity LT of said objective lens is estimated by using driving current on the tilt side of said movable tilting means or driving voltage on the tilt side of said movable tilting means.
A still further aspect of the present invention is the optical disk device, wherein set values of said coefficient xcex2 and said coefficient xcex3 are changed depending on whether said optical spot scans on said cyclic grooves or on said cyclic inter-groove spaces.
A still yet further aspect of the present invention is the optical disk device, wherein
tilt to an optical axis of said objective lens converging as a result of control agrees with the tilting direction of a base plate of said optical disk, and
a third order coma aberration component of an optical spot on said signal surface is substantially suppressed by setting of said coefficient xcex2 with each tilt.
An additional aspect of the present invention is the optical disk device, wherein an alignment error to cyclic grooves or cyclic inter-groove spaces of said optical spot converging as a result of control is substantially suppressed by setting of said coefficient xcex3.
A still additional aspect of the present invention is the optical disk device, wherein
said optical detecting means is divided into two by a straight line corresponding to the rotational direction of said optical disk, and can detect a difference signal from the divided areas, and
either said signal A or said signal B is said difference signal at the time when said optical spot scans on said cyclic grooves or said cyclic inter-groove spaces.
A yet additional aspect of the present invention is the optical disk device, wherein
when letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be A1, and a detecting level of an envelope drawn by a side with a larger detected light quantity be A2 between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits a, and
letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be B1, and a detecting level of an envelope drawn by a side with a larger detected light quantity be B2 between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits b,
said signal A is expressed by any one of A=A1xe2x88x92B1, A=A2xe2x88x92B2, and A=(A2xe2x88x92A1)xe2x88x92(B2xe2x88x92B1).
A still yet additional aspect of the present invention is the optical disk device, wherein
when letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be A1, and a detecting level of an envelope drawn by a side with a larger detected light quantity be A2 between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits a, and
letting a detecting level of an envelope drawn by a side with a smaller detected light quantity be B1, and a detecting level of an envelope drawn by a side with a larger detected light quantity be B2 between detected signal waveforms by said optical detecting means when said optical spot scans near said cyclic pits b,
said signal B is expressed by any one of B=A1xe2x88x92B1, B=A2xe2x88x92B2, and B=(A2xe2x88x92A1)xe2x88x92(B2xe2x88x92B1).
A supplementary aspect of the present invention is the optical disk device, wherein
said signal A is said difference signal, and
a pit along the rotational direction of said optical disk is formed on the inner peripheral side of said optical disk, and
said movable tilting means tilts said objective lens so that a detected signal amplitude at the time when said optical spot scans on said pit may be maximum, and moves said optical spot onto said cyclic grooves or said cyclic inter-groove spaces while keeping tilt of said objective lens, and detects an output level of said signal A when said compensated signal (B-xcex3xc2x7LT) becomes zero, and uses a value made by subtracting an offset quantity because of an adjusting error from an output level of said detected signal A, instead of said signal A.
A still supplementary of the present invention is a control method of an optical system, comprising the steps of:
condensing radiated light from a light source on an optical information recording medium by using a given optical system;
detecting reflected light from said optical information recording medium; and
performing tracking control and/or tilting control of said optical system on the basis of said detected light, wherein said control is performed by using an off-track quantity and/or a tilt quantity of said optical system.
A yet supplementary aspect of the present invention is a medium that carries a program and/or data for executing by a computer all or part of functions of all or part of means of the present invention, wherein said medium can be processed by a computer.